Chapter 23 Microbial Diseases of the Cardiovascular and Lymphatic Systems Flashcards

As the blood circulates, some blood plasma filters
out of the blood capillaries into spaces between tissue cells

The circulating fluid

Microscopic lymphatic vessels that surround tissue cells

At times the lymph nodes themselves get
infected and become visibly swollen and tender; swollen lymph
nodes

Lymph nodes are also an important component of the
body’s immune system. Foreign microbes entering lymph nodes
encounter two types of lymphocytes: B cells, which are stimulated
to become plasma cells that produce humoral antibodies; and
T cells, which then differentiate into effector T cells that are
essential to the cell-mediated immune system

An acute illness that is associated
with the presence and persistence of pathogenic microorganisms
or their toxins in the blood is termed septicemia

as a systemic inflammatory response syndrome (SIRS) caused by
a focus of infection that releases mediators of inflammation into
the bloodstream

The SIRS must exhibit at least two of a set
of defined conditions: fever, rapid heart or respiratory rates, and a
high count of white blood cells

Sepsis and septicemia are
often accompanied by the appearance of lymphangitis, inflamed
lymph vessels visible as red streaks under the skin, running along
the arm or leg from the site of the infection

When sepsis results in a drop in blood pressure
(shock) and dysfunction of at least one organ, it is considered to
be severe sepsis

Septic shock is most likely to be caused by gram-negative
bacteria

cell walls of many gram-negative
bacteria (LPS; see page 86) contain endotoxins that are released
upon lysis of the cell.

These endotoxins can cause a severe drop
in blood pressure with its associated signs and symptoms.

Septic
shock is often called by the alternative names gram-negative
sepsis or endotoxic shock.

In addition to antibiotics, treatment of septic shock involves
attempts to neutralize the LPS components and inflammationcausing
cytokines.

The U.S. Food and Drug Administration
(FDA) has approved a drug, drotrecogin alfa (Xigris), which is
the first to reduce the death rate of sepsis cases

Gram-positive bacteria are now the most common cause of sepsis.

Both staphylococci and streptococci produce potent exotoxins that
cause toxic shock syndrome, a toxemia

The frequent use of invasive procedures in hospitals
allows gram-positive bacteria to enter the bloodstream.

An especially important group of gram-positive bacteria
are the enterococci, which are responsible for many nosocomial
infections.

The enterococci are inhabitants of the human colon
and frequently contaminate skin.

Enterococcus faecium and
Enterococcus faecalis, are now recognized as leading causes
of nosocomial infections of wounds and the urinary tract.

Enterococci have a natural resistance to penicillin and have
rapidly acquired resistance to other antibiotics

S. agalactiae
(ā´gal-act-ē-ī) is the only GBS and is the most common cause
of life-threatening neonatal sepsis.

a nosocomial infection.

It begins as an infection of
the uterus as a result of childbirth or abortion. Streptococcus
pyogenes, a group A beta-hemolytic streptococcus, is the most
frequent cause

Puerperal sepsis progresses from an infection of the uterus
to an infection of the abdominal cavity (peritonitis) and in
many cases to sepsis

The SIRS must exhibit at least two of a set
of defined conditions: fever, rapid heart or respiratory rates, and a
high count of white blood cells.

both

is characterized by fever, general weakness, and heart murmur.

It is usually caused by alpha-hemolytic streptococci such as are
common in the oral cavity

usually caused by alpha-hemolytic streptococci such as are
common in the oral cavity

which is usually caused by Staphylococcus
aureus.

The organisms find their way from the initial
site of infection to normal or abnormal heart valves; the rapid
destruction of the heart valves is frequently fatal within a few days
or weeks if untreated

can also cause pericarditis,
inflammation of the sac around the heart (the pericardium

Microorganisms are released by tooth extractions or
tonsillectomies, enter the blood, and find their way to the heart

Streptococcal infections, such as those caused by Streptococcus
pyogenes, sometimes lead to rheumatic fever, which is generally
considered an autoimmune complication

Subcutaneous nodules at joints often accompany
this stage (Figure 23.5).

In about half of persons affected, an inflammation
of the heart, probably from a misdirected immune reaction
against streptococcal M protein, damages the valves.

As many as 10% of people with rheumatic fever develop
Sydenham’s chorea, an unusual complication known in the
Middle Ages as Saint Vitus’ dance

Several months following
an episode of rheumatic fever, the patient (much more likely to
be a girl than a boy) exhibits purposeless, involuntary movements
during waking hours.

Occasionally, sedation is required
to prevent self-injury from flailing arms and legs. The condition
disappears after a few months

an example of a zoonotic disease, that is, a disease
transmitted by contact with infected animals, most commonly
rabbits and ground squirrels

an example of a zoonotic disease, that is, a disease
transmitted by contact with infected animals, most commonly
rabbits and ground squirrels

The pathogen is Francisella tularensis,
a small gram-negative bacillus. It can enter humans by several
routes.

The most common is penetration of the skin at a minor
abrasion, where it creates an ulcer at the site.

About a week after
infection, the regional lymph nodes enlarge; many will contain
pockets of pus.

The bacterium can multiply
in macrophages—as much as a thousand-fold

Tularemia is also transmitted in some areas by ticks and insects
and is known there as deer fly fever

Antibiotics such as tetracycline, administered
for 10 to 15 days, are an effective treatment

rabbits

With over 500,000 new human cases annually, brucellosis is
the world’s most common bacterial zoonosis

Brucella bacteria are small, aerobic, gram-negative coccoid
rods

Typically they include fever (often rising and falling, which has
given the disease an alternative name of undulant fever), malaise,
night sweats, and muscle aches

Antibiotic therapy is possible, and the bacteria have not
shown development of resistance.

However, treatment must be
very long term, usually at least 6 weeks, and involves a combination
of at least two antibiotics

Mediterranean and in southeastern Europe, Asia, Latin
America, and the Caribbean

The endospore-forming bacillus
is a large, aerobic, gram-positive microorganism that is apparently
able to grow slowly in soil types having specific moisture conditions.

The endospores have survived in tests in soil for up to
60 years. The disease strikes primarily grazing animals, such as
cattle and sheep.

The B. anthracis endospores are ingested along
with grasses, causing a fulminating, fatal sepsis

capsule of B. anthracis is very unusual.
It is not a polysaccharide but rather is composed of amino acid
residues, which for some reason do not stimulate a protective
response by the immune system

If a wound causes the blood supply to be interrupted, a condition
known as ischemia, the wound becomes anaerobic.

Ischemia leads
to necrosis, or death of the tissue.

The death of soft tissue resulting
from the loss of blood supply is called gangrene

Once ischemia and the subsequent necrosis caused by
impaired blood supply have developed, gas gangrene can develop,
especially in muscle tissue

C. perfringens microorganisms
grow, they ferment carbohydrates in the tissue and produce gases
(carbon dioxide and hydrogen) that swell the tissue.

The bacteria
produce toxins that move along muscle bundles, killing cells
and producing necrotic tissue that is favorable for further growth

The oxygen
saturates the infected tissues and thereby prevents the growth of
the obligately anaerobic clostridia

a gram-negative rod
similar to the Yersinia bacterium that causes plague (page 655).
P. multocida is primarily a pathogen of animals, and it causes
sepsis (hence the name multocida, meaning many-killing).

The pathogen
is an aerobic, gram-negative bacterium, Bartonella henselae
(bärʹto-nel-lä henʹsel-Ī).

Microscopy shows that the bacterium
can inhabit the interior of some cat red blood cells.

It is connected
to the exterior of the cell and to the surrounding extracellular
fluid by a pore

Bartonella henselae, the pathogen of cat-scratch disease,
is capable of growth in what insect?

all
members of the spirochete genus Borrelia cause relapsing fever.
In
the United States, the disease is transmitted by soft ticks that feed on
rodents.

The incidence of relapsing fever increases during the summer
months, when the activity of rodents and arthropods increases

The disease is characterized by fever, sometimes in excess of
40.5°C, jaundice, and rose-colored skin spots. After 3 to 5 days,
the fever subsides.

Three or four relapses may occur, each
shorter and less severe than the initial fever.

Each recurrence
is caused by a different antigenic type of the spirochete, which
evades existing immunity.

Borrelia burgdorferi was identified as
the cause. Lyme disease may now be the most common tickborne
disease in the United States. In Europe and Asia, the disease is
usually known as Lyme borreliosis.

caused by
Ehrlichia chafeensis (erʹlik-ē-ä chafʹē-en-sis). This is a gramnegative,
rickettsia-like, obligately intracellular bacterium

was formerly called human granulocytic
ehrlichiosis. The change occurred when the causative organism,
an obligate intracellular bacterium formerly grouped with the
ehrlichia, was renamed Anaplasma phagocytophilum (anʹä-plaz-mä

The various typhus diseases are caused by rickettsias, bacteria
that are obligate intracellular parasites of eukaryotes.

Rickettsias,
which are spread by arthropod vectors, infect mostly the endothelial
cells of the vascular system and multiply within them

This rickettsia is a parasite of ticks and is usually
passed from one generation of ticks to another through their
eggs, a mechanism

field mice

Rocky Mountain spotted fever

mosquito-borne malarial
infections apparently foster the development of Burkitt’s lymphoma
by impairing the immune response to EB virus, which is
almost universally present in human adults worldwide

infected B cells produce heterophile
antibodies

(tumors
of the spleen, lymph nodes, or liver)

(nose
and pharynx) cancer among certain ethnic groups in southeast
Asia and Inuits.

cytomegalovirus

About 85% of AIDS patients
exhibit a CMV-caused eye infection,

The symptoms are a high fever and severe,
crippling joint pains—especially in the wrists, fingers, and
ankles—that can persist for weeks or months. There is often a
rash and even massive blisters.

The death rate is very low.

The
vector is the Aedes mosquito, primarily Aedes aegypti (āʹe-dēz
ē-jipʹtē), which spreads the disease widely in Asia and Africa